Measuring systems of the above mentioned kind are used for example for monitoring the concentration of certain substances in body fluids, for example for blood sugar determination. Test strips of different manufacturing batches can have calibration data which deviates from one test strip to another. Therefore, this calibration data must be communicated to the measuring device before the carrying out of the measurement. It is also possible that one such measuring device is suited to the carrying out of different measurements. If so the measuring device must be informed before the insertion of the test strip, for which particular measurement the inserted test strip is intended. This data is generally stored in the code carrier. There exists non-authorized suppliers, who attempt to deliver test strips by themselves for systems of the previously mentioned kind. Since the calibration data of given test strips do not differ grossly from batch to batch, these suppliers may try to copy the code carrier, including the coded information, even if they can not read the coded information. In view of this the measuring accuracy of the measuring systems suffers with corresponding danger for patients who use such a measuring system.
The invention has as its object to hinder the copying of the code carriers with their own coded information, or to see to it that such duplicated code carriers are unuseful.